Contact type battery baking method

Abstract

The invention discloses a contact type battery baking method, and relates to the technical field of battery baking processes. The method specifically comprises the following steps: heating a laminated battery cell in a normal-pressure oven, and stopping preheating when the internal temperature of the battery cell reaches a preset temperature; the air pressure in the oven is reduced to the target air pressure, gradient heating baking is carried out under the target air pressure, and in the gradient heating baking period, dry compressed air is adopted to implement dynamic gas replacement; and releasing the vacuum after the vacuum baking is continued for a preset time, so that the water content of the battery cell meets a preset value. The drying efficiency is improved, the cost is reduced, and meanwhile it is ensured that the moisture of the dried battery reaches the standard.

Description

Technical Field

[0001] The invention relates to the technical field of battery baking technology, and in particular to a contact type battery baking method. Background Art

[0002] With the advancement of science and technology and the rapid development of the battery industry, especially the widespread application of lithium batteries, the performance and safety of batteries have received increasing attention. In the production process of batteries, the drying process is one of the most important links, especially for the control of the electrolyte of lithium batteries and the moisture inside the battery. If the moisture content inside the battery is still high after drying, especially when the electrolyte in the battery encounters moisture, a decomposition reaction will occur, releasing corrosive hydrogen fluoride gas (HF). HF gas reacts with the components inside the battery, such as Li in the SEI film. 2 CO 3 The reaction products are deposited on the negative electrode surface, which greatly increases the resistance of the electrode interface, resulting in a decrease in the battery's specific capacity and cycle performance. In addition, the reversibility of the battery's passivation film will also be reduced, further affecting the overall performance and service life of the battery.

[0003] In order to avoid the above problems, many battery production lines currently use vacuum direct drying. Vacuum direct drying can effectively remove moisture from the battery and can more accurately control the moisture content to ensure that the moisture content of the battery after drying meets the standards. Although vacuum direct drying has a good effect in moisture control. However, vacuum drying requires maintaining a low pressure environment and high temperature heating at the same time. The operation and maintenance costs of vacuum equipment are high, and the exhaust efficiency of the vacuum pump is low, resulting in a long drying process, low drying efficiency, and high production costs.

[0004] Therefore, how to improve drying efficiency, reduce costs, and at the same time ensure that the moisture content of the battery meets the standards after drying has become a technical problem that needs to be urgently solved in the battery production field. Summary of the invention

[0005] The main purpose of the present invention is to provide a contact type battery baking method, aiming to improve the drying efficiency, reduce the cost, and ensure that the moisture content of the battery after drying meets the standard.

[0006] In order to achieve the above object, the present invention provides a contact type battery baking method, comprising the following steps: The stacked battery cells are placed in a normal pressure oven for heating, and the preheating is terminated when the internal temperature of the battery cells reaches the preset temperature; The air pressure in the oven is reduced to the target air pressure, and gradient temperature baking is performed under the target air pressure. During the gradient temperature baking, dynamic gas replacement is performed using dry compressed air; After the vacuum baking is continued for a predetermined time, the vacuum is released so that the water content of the battery cell meets the preset value.

[0007] It can effectively control the temperature and pressure changes of the battery cell during the baking process, ensure the uniform removal of moisture inside the battery cell, and replace nitrogen with dry compressed air for gas replacement, thereby reducing costs and improving baking efficiency. By precisely controlling the gradient temperature rise and dynamic gas replacement, it can minimize overheating or local over-drying during the baking process, improve the baking quality of the battery cell, and effectively shorten the baking cycle.

[0008] In one embodiment of the present application, when the laminated battery cell is a ternary lithium-ion battery, the preset temperature is 97°C.

[0009] Setting the temperature to 97°C can reduce energy consumption during the drying process, further reducing production costs.

[0010] In one embodiment of the present application, the target air pressure is A, 70pa≥A≥20pa.

[0011] It can effectively control the water evaporation process under different target air pressures. By precisely adjusting the air pressure range, it can ensure efficient water removal while avoiding damage to the battery cell structure, thereby improving the stability of the baking process and the performance consistency of the battery cells.

[0012] In one embodiment of the present application, the target air pressure is 50 Pa.

[0013] By controlling the air pressure at a set value of 50pa, the baking process is more precise, which can effectively reduce the baking time and improve the baking quality.

[0014] In an embodiment of the present application, the predetermined time is 8 hours.

[0015] It is possible to efficiently remove moisture from the battery cells within 8 hours of vacuum baking, ensuring that the battery cells meet the preset moisture standards and reducing energy consumption.

[0016] In one embodiment of the present application, the ternary lithium-ion battery adopts a quadruple composite structure of nine layers of positive electrode sheets, two layers of ceramic diaphragms, one layer of negative electrode sheet, and one layer of base film.

[0017] The performance and safety of ternary lithium-ion batteries can be effectively improved by adopting a four-layer composite structure of nine positive electrode sheets, two ceramic diaphragms, one negative electrode sheet, and one base film. The increase in the number of positive electrode sheets helps to increase the energy density of the battery, while the use of ceramic diaphragms improves the thermal stability and safety of the battery and reduces the risk of short circuits.

[0018] In one embodiment of the present application, when the target air pressure A is less than 20 Pa, dry compressed air is input into the oven.

[0019] When the target air pressure A is less than 20 Pa, by inputting dry compressed air into the oven, not only can the negative impact of too low air pressure on the baking effect be avoided, but also the stability of the baking process can be maintained.

[0020] In one embodiment of the present application, when the target gas pressure is greater than 70 Pa, the gas in the oven is extracted to reduce the gas pressure in the oven.

[0021] When the target pressure is greater than 70Pa, the gas in the oven is evacuated and the pressure is reduced to effectively prevent the excessive pressure from causing reduced water evaporation efficiency or uneven baking. The adjustment of the vacuum degree ensures that the water evaporates quickly at a lower pressure, thereby accelerating the water removal process and improving the baking efficiency.

[0022] In an embodiment of the present application, the preset value is B, where B<200 ppm.

[0023] By precisely controlling the moisture content, performance loss or safety risks caused by excessive moisture in the battery cell can be avoided. By setting the B value to less than 200ppm, the battery can be guaranteed to have better electrochemical performance, higher safety and longer service life during use.

[0024] The above technical solution can effectively control the temperature and air pressure changes of the battery cell during the baking process, ensure the uniform removal of moisture inside the battery cell, and replace nitrogen with dry compressed air for gas replacement, thereby reducing costs and improving baking efficiency. By precisely controlling the gradient temperature rise and dynamic gas replacement, overheating or local over-drying during the baking process can be minimized, the baking quality of the battery cell can be improved, and the baking cycle can be effectively shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 This is a schematic diagram of the process structure of the first embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and do not constitute a limitation to the present invention.

[0027] like Figure 1 As shown, in order to achieve the above purpose, the present invention provides a contact type battery baking method, comprising the following steps: The stacked battery cells are placed in a normal pressure oven for heating, and the preheating is terminated when the internal temperature of the battery cells reaches the preset temperature; The air pressure in the oven is reduced to the target air pressure, and gradient temperature baking is performed under the target air pressure. During the gradient temperature baking, dynamic gas replacement is performed using dry compressed air; After the vacuum baking is continued for a predetermined time, the vacuum is released so that the water content of the battery cell meets the preset value.

[0028] Specifically, first, the temperature inside the battery cell is heated by the heating system of the atmospheric pressure oven, and the temperature inside the battery cell is monitored by the temperature control system and compared with the preset temperature. When the temperature inside the battery cell reaches the preset temperature, the preheating stage in the atmospheric pressure oven is terminated by the automatic control system. After that, the air pressure in the oven is reduced to the target air pressure, and the air pressure is adjusted by the control valve and the vacuum pump. After the air pressure drops to the target air pressure, the gradient temperature rise baking stage is entered. In this stage, the heating temperature is precisely controlled to gradually heat the battery cell within a certain period of time to ensure that the temperature changes smoothly and evenly during the baking process. In order to ensure better gas flow and effective discharge of moisture during baking, dynamic gas replacement is implemented by dry compressed air. Specifically, dry compressed air enters the oven through the gas input device, contacts the surface of the battery cell, continuously replaces the air in the oven, and ensures that moisture is discharged in time. The time for continuous vacuum baking is set according to the specific type, specification and moisture content of the battery cell. After this stage, the vacuum is released by the control system, and the water content of the battery cell is detected to ensure that the moisture reaches the preset standard value.

[0029] The above technical solution can effectively control the temperature and air pressure changes of the battery cell during the baking process, ensure the uniform removal of moisture inside the battery cell, and replace nitrogen with dry compressed air for gas replacement, thereby reducing costs and improving baking efficiency. By precisely controlling the gradient temperature rise and dynamic gas replacement, overheating or local over-drying during the baking process can be minimized, the baking quality of the battery cell can be improved, and the baking cycle can be effectively shortened.

[0030] In one embodiment of the present application, when the laminated battery cell is a ternary lithium-ion battery, the preset temperature is 97°C.

[0031] Specifically, when the laminated battery cell is a ternary lithium-ion battery, the battery cell is placed in a normal pressure oven for heating, and the temperature inside the battery cell is monitored in real time by a temperature control system. When the temperature inside the battery cell reaches 97°C, the temperature rise inside the battery is significantly slow, the preheating stage is immediately terminated, and the next operation stage is entered. The temperature control system accurately controls the heating system to stop heating according to the real-time changes in the temperature inside the battery cell, thereby ensuring that the battery cell completes the preheating process at a predetermined temperature.

[0032] By adopting the above technical solution and setting the temperature to 97°C, the energy consumption during the drying process can be reduced, further reducing the production cost.

[0033] In one embodiment of the present application, the target air pressure is A, 70pa≥A≥20pa.

[0034] Specifically, the target air pressure is set to A, where the range of A is between 20 Pa and 70 Pa. In order to better illustrate the application of the air pressure range, the following examples illustrate the two end points of the air pressure range: When the target air pressure A is set to 20Pa, the air pressure inside the oven is reduced to 20Pa through the vacuum pump and the air pressure regulating device. Under this air pressure, the boiling point of water is significantly reduced, so that the water inside the battery cell can evaporate quickly at a lower temperature, thereby speeding up the water removal process. It can improve baking efficiency and shorten baking time.

[0035] When the target air pressure A is set to 70Pa, the air pressure inside the oven drops to 70Pa. At this higher air pressure, the rate of water evaporation is relatively low, which is suitable for processing batteries with low moisture content. The higher air pressure at this time can avoid excessive evaporation caused by too low air pressure, ensuring that the temperature and air pressure changes during the baking process are more stable.

[0036] By adopting the above technical solution, the water evaporation process can be effectively controlled under different target air pressures. By accurately adjusting the air pressure range, while ensuring efficient water removal, damage to the battery cell structure is avoided, thereby improving the stability of the baking process and the performance consistency of the battery cells.

[0037] In one embodiment of the present application, the target air pressure is 50 Pa.

[0038] Specifically, the target air pressure is set to 50 Pa. During the baking process, the air pressure inside the oven is first reduced to 50 Pa through a vacuum pump and an air pressure regulating device. Under this air pressure, the boiling point of water is reduced, which promotes the efficient evaporation of water inside the battery cell. During the gradient temperature baking stage, the air pressure in the oven is maintained at 50 Pa, ensuring that the water can evaporate quickly at a lower temperature and avoiding excessive evaporation due to too low air pressure, thereby ensuring the stability of the baking process.

[0039] By adopting the above technical solution, by controlling the air pressure at a set value of 50 Pa, the baking process is more precise, which can effectively reduce the baking time and improve the baking quality.

[0040] In an embodiment of the present application, the predetermined time is 8 hours.

[0041] Specifically, the scheduled time for continuous vacuum baking is 8 hours. During the baking process, the battery cell is vacuum-baked at a target air pressure of 50pa, and the baking time is set to 8 hours. During the vacuum baking, the moisture inside the battery cell gradually evaporates through the low-pressure environment, ensuring that the moisture is quickly and evenly discharged from the inside of the battery cell. The control of temperature and air pressure during the entire baking process can effectively remove moisture from the battery cell within 8 hours and ensure that the physical and chemical properties of the battery cell are not damaged.

[0042] By adopting the above technical solution, it is possible to efficiently remove moisture from the battery cells within 8 hours of vacuum baking, ensuring that the battery cells meet the preset moisture standards and reducing energy consumption.

[0043] In one embodiment of the present application, the ternary lithium-ion battery adopts a quadruple composite structure of nine layers of positive electrode sheets, two layers of ceramic diaphragms, one layer of negative electrode sheet, and one layer of base film.

[0044] Specifically, nine layers of positive electrode sheets are first stacked layer by layer to ensure uniform distribution of positive electrode materials. Then, two layers of ceramic diaphragms are added. The ceramic diaphragms play an isolating role for the electrolyte inside the battery and can effectively enhance the thermal stability of the battery. Then a layer of negative electrode sheet is stacked, and finally a layer of base film is placed on the outermost layer. The base film is mainly used to improve the mechanical strength and stability of the battery and prevent the battery from deforming during use.

[0045] The above technical solution can effectively improve the performance and safety of ternary lithium-ion batteries by adopting a four-layer composite structure of nine positive electrode sheets, two ceramic diaphragms, one negative electrode sheet, and one base film. The increase in the number of positive electrode sheets helps to increase the energy density of the battery, while the use of ceramic diaphragms improves the thermal stability and safety of the battery and reduces the risk of short circuits.

[0046] In one embodiment of the present application, when the target air pressure A is less than 20 Pa, dry compressed air is input into the oven.

[0047] Specifically, when the air pressure drops below 20pa, dry compressed air is automatically input into the oven. The dry compressed air continuously enters the oven through the gas input device, contacts the surface of the battery cell, helps to discharge the moisture in the oven, and ensures the continuous evaporation of the water in the battery cell.

[0048] By adopting the above technical solution, when the target air pressure A is less than 20 Pa, by inputting dry compressed air into the oven, not only the negative impact of too low air pressure on the baking effect can be avoided, but also the stability of the baking process can be maintained.

[0049] In one embodiment of the present application, when the target gas pressure is greater than 70 Pa, the gas in the oven is extracted to reduce the gas pressure in the oven.

[0050] Specifically, if the pressure in the oven exceeds 70Pa, the control system will automatically start the vacuum pump to extract the gas in the oven to reduce the pressure to the target pressure range. By continuously pumping air, the pressure in the oven will be effectively reduced to ensure that the pressure is always kept within the predetermined range to promote the rapid evaporation of water inside the battery cell.

[0051] By adopting the above technical solution, when the target air pressure is greater than 70Pa, the air in the oven is evacuated and the air pressure is reduced, which can effectively prevent the air pressure from being too high, resulting in reduced water evaporation efficiency or uneven baking. The adjustment of the vacuum degree ensures that the water evaporates quickly at a lower air pressure, thereby accelerating the water removal process and improving the baking efficiency.

[0052] In an embodiment of the present application, the preset value is B, where B<200 ppm.

[0053] Specifically, the preset value is set to B, where the value of B is less than 200ppm. After the baking process is completed, the moisture content of the battery cell will be measured and monitored. By using humidity detection equipment or other appropriate detection means, the moisture content in the battery cell is monitored in real time. When the moisture content reaches or is lower than B (i.e., less than 200ppm), the baking process will be terminated to ensure that the battery cell meets the preset moisture standard.

[0054] By adopting the above technical solution, the water content is precisely controlled to avoid performance loss or safety risks caused by excessive water in the battery cell. By setting the B value to less than 200ppm, the battery is ensured to have better electrochemical performance, higher safety and longer service life during use.

[0055] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A contact battery baking method, characterized in that: The following steps are involved: The stacked battery cells are placed in a normal pressure oven for heating, and the preheating is terminated when the internal temperature of the battery cells reaches the preset temperature; The air pressure in the oven is reduced to the target air pressure, and gradient temperature baking is performed under the target air pressure. During the gradient temperature baking, dynamic gas replacement is performed using dry compressed air; After the vacuum baking is continued for a predetermined time, the vacuum is released so that the water content of the battery cell meets the preset value.

2. The contact battery baking method according to claim 1, characterized in that: When the laminated battery cell is a ternary lithium-ion battery, the preset temperature is 97°C.

3. The contact battery baking method according to claim 2, characterized in that: The target air pressure is A, 70pa≥A≥20pa.

4. The contact battery baking method according to claim 3, characterized in that: The target air pressure is 50 Pa.

5. The contact type battery baking method according to claim 2, characterized in that: The predetermined time is 8 hours.

6. The contact type battery baking method according to claim 2, characterized in that: The ternary lithium-ion battery adopts a quadruple composite structure of nine layers of positive electrode sheets, two layers of ceramic diaphragms, one layer of negative electrode sheet, and one layer of base film.

7. The contact battery baking method according to claim 3, characterized in that: When the target air pressure A is less than 20 Pa, dry compressed air is input into the oven.

8. The contact battery baking method according to claim 3, characterized in that: When the target gas pressure is greater than 70 Pa, the gas in the oven is evacuated to reduce the gas pressure in the oven.

9. The contact battery baking method according to claim 2, characterized in that: The default value is B, B<200ppm.

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